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Study of Collimated Neutron Flux Monitors for MAST and MAST Upgrade
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Measurements of the neutron emission, resulting from nuclear fusion reactions between the hydrogen isotopes deuterium and tritium, can provide a wealth of information on the confinement properties of fusion plasmas and how these are affected by Magneto-Hydro-Dynamic (MHD) instabilities.

This thesis describes work aimed to develop neutron measurement techniques for nuclear fusion plasma experiments, specifically regarding the performance and design of collimated neutron flux monitors (neutron cameras) for the Mega Ampere Spherical Tokamak, MAST, and for MAST Upgrade. The first part of the thesis focuses on the characterization of a prototype neutron camera installed at MAST and provides an account of the very first measurements of the neutron emissivity along its collimated fields of view. It is shown that the camera has sufficient temporal and spatial resolution to measure the effect of MHD instabilities on the neutron emissivity. The neutron camera fulfils the requirement on the measurements of the neutron count rate profile with less than 10 % statistical uncertainty in a time resolution of 1 ms. The instrument's more rudimentary capabilities to provide information on the neutron energy distribution are also presented and discussed. The encouraging results obtained with the prototype neutron camera show the potential of a collimated neutron flux monitor at MAST and suggest that an upgraded instrument for MAST Upgrade will provide crucial information on fast ions behavior and other relevant physics issues.

The design of such an upgraded instrument for MAST Upgrade is discussed in the second part of the thesis. Two design options are explored, one consisting of two collimator arrays in the horizontal direction, another more traditional design with lines-of-sight in the poloidal cross section plane. On the basis of the experience gained with the prototype neutron camera and on the exploratory design and estimated performance for the upgraded camera presented here, a conceptual design of a neutron camera upgrade is proposed.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. , 84 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1141
Keyword [en]
Fusion, Plasma diagnostics, Neutron camera, collimated neutron flux monitor, MAST, MAST Upgrade, ITER
National Category
Fusion, Plasma and Space Physics
Research subject
Applied Nuclear Physics
Identifiers
URN: urn:nbn:se:uu:diva-221591ISBN: 978-91-554-8930-4 (print)OAI: oai:DiVA.org:uu-221591DiVA: diva2:709644
Public defence
2014-05-27, Häggsalen, Ångströmlaboratoriet, Uppsala, 10:00 (English)
Supervisors
Available from: 2014-05-05 Created: 2014-04-02 Last updated: 2014-06-30
List of papers
1. Study of the detector efficiency of MAST neutron camera
Open this publication in new window or tab >>Study of the detector efficiency of MAST neutron camera
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2012 (English)Conference paper, Published paper (Other academic)
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-221549 (URN)
Conference
39th EPS Conference & 16th Int. Congress on Plasma Phys. Stockholm, July 2-6, 2012 ECA Vol.36F, P-2.084
Available from: 2014-04-02 Created: 2014-04-01 Last updated: 2014-06-11
2. The 2.5 MeV neutron flux monitor for MAST
Open this publication in new window or tab >>The 2.5 MeV neutron flux monitor for MAST
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2014 (English)In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 753, 72-83 p.Article in journal (Refereed) Published
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-221553 (URN)10.1016/j.nima.2014.03.060 (DOI)000336547500010 ()
Available from: 2014-04-02 Created: 2014-04-01 Last updated: 2017-12-05Bibliographically approved
3. Observation of fast ion behaviour with a neutron emission profile monitor in MAST
Open this publication in new window or tab >>Observation of fast ion behaviour with a neutron emission profile monitor in MAST
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2012 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 52, no 9, 094015- p.Article in journal (Refereed) Published
Abstract [en]

Preliminary measurements of neutron emissivity at the Mega Amp Spherical Tokamak (MAST) along collimated lines-of-sight showa clear correlation between the neutron emissivity temporal and spatial evolution and the evolution of different MHD instabilities. In particular, the variations in neutron emissivity during sawtooth oscillations are compared with changes in the classical fast ion slowing-down time, while fast ion losses are observed in bursts during fishbones or as a continuous process during long-lived modes.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-183788 (URN)10.1088/0029-5515/52/9/094015 (DOI)000308810100016 ()
Conference
12th IAEA Technical Meeting on Energetic Particles in Magnetic Confinement Systems / 5th IAEA Technical Meeting on Theory of Plasma Wave Instabilities, SEP 05-11, 2011, Austin, TX
Available from: 2012-11-01 Created: 2012-11-01 Last updated: 2017-12-07Bibliographically approved
4. Validation of neutron emission profiles in MAST with a collimated neutron monitor
Open this publication in new window or tab >>Validation of neutron emission profiles in MAST with a collimated neutron monitor
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2012 (English)In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 83, no 10, 10D910- p.Article in journal, Meeting abstract (Refereed) Published
Abstract [en]

A neutron camera with liquid scintillator detectors is used in MAST to measure the neutron emissivity from D(d,n) 3He reactions along collimated lines of sight. In this work, the measured recoil proton pulse height spectra generated in the detectors by the incident neutrons is modelled taking into account the energy spectrum of the generated neutrons, their spatial distribution and transport to the detectors as well as the detectors response function. The contribution of scattered neutrons to the pulse height spectrum is also modelled. Good agreement is found between the experimental data and the simulations. Examples are given showing the sensitivity of the recoil proton pulse height spectra to different observation angles with respect the neutral beam injection and the plasma rotation direction.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-186840 (URN)10.1063/1.4732059 (DOI)000311562900098 ()
Conference
THE 19TH TOPICAL CONFERENCE ON HIGH-TEMPERATURE PLASMA DIAGNOSTICS, May 6-10, 2012, Monterey, CA, USA
Available from: 2012-12-06 Created: 2012-11-29 Last updated: 2017-12-07Bibliographically approved
5. A poloidal section neutron camera for MAST Upgrade
Open this publication in new window or tab >>A poloidal section neutron camera for MAST Upgrade
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2014 (English)In: Fusion Reactor Diagnostics / [ed] Gorini, G; Orsitto, FP; Sozzi, C; Tardocchi, M, 2014, 129-132 p.Conference paper, Published paper (Other academic)
Abstract [en]

The Mega Ampere Spherical Tokamak Upgrade (MAST Upgrade) is intended as a demonstration of the physics viability of the Spherical Tokamak (ST) concept and as a platform for contributing to ITER/DEMO physics. Concerning physics exploitation, MAST Upgrade plasma scenarios can contribute to the ITER Tokamak physics particularly in the field of fast particle behavior and current drive studies. At present, MAST is equipped with a prototype neutron camera (NC). On the basis of the experience and results from previous experimental campaigns using the NC, the conceptual design of a neutron camera upgrade (NC Upgrade) is being developed. As part of the MAST Upgrade, the NC Upgrade is considered a high priority diagnostic since it would allow studies in the field of fast ions and current drive with good temporal and spatial resolution. In this paper, we explore an optional design with the camera array viewing the poloidal section of the plasma from different directions.

Series
AIP Conference Proceedings, ISSN 0094-243X ; 1612
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-221558 (URN)10.1063/1.4894039 (DOI)000343712300024 ()978-0-7354-1248-4 (ISBN)
Conference
International Conference on Fusion Reactor Diagnostics, SEP 09-13, 2013, Varenna, ITALY
Available from: 2014-04-02 Created: 2014-04-01 Last updated: 2014-12-11Bibliographically approved
6. Conceptual design of the 2.5 MeV neutron flux monitor for MAST Upgrade
Open this publication in new window or tab >>Conceptual design of the 2.5 MeV neutron flux monitor for MAST Upgrade
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(English)Manuscript (preprint) (Other academic)
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-221559 (URN)
Available from: 2014-04-02 Created: 2014-04-01 Last updated: 2014-06-11

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